Electrical control system



Nov. 17, 1936. E. J. DILLMAN I ELECTRICAL CONTROL SYSTEM Filed June 29,1934 INVENTOR 6% BY ATT NEY Patented Nov. 17, 1936 PATENT OFFICEELECTRICAL CONTROL SYSTEM Earnest J. Dillman, Detroit, Mich., assignorto Detroit Lubricator Company, Detroit, Mich., a

corporation of Michigan Application June 29, 1934, Serial No. 732,975

3 Claims.

My invention relates to new and useful improvements in an electricalcontrol system wherein a temperature responsive switch is employed tocontrol the operation of an electrically operated means.

An object of my invention is to provide the system with means by whichthe set or predetermined differential of operation of the switch may beregulated or controlled.

Another object is to provide means by which the set or predetermineddifferential of operation of the switch may be maintained irrespectiveof variation or change in the resistance of the electrically operatedmeans controlled by the switch. 3

The invention consists in the novel system and the controlling means forswitch operation, to be more fully described hereinafter and the noveltyof which will be particularly pointed out and distinctly claimed.

In the accompanying drawing, to be taken as a part of thisspecification, I have fully and clearly illustrated a preferredembodiment of my invention, in which drawing" The figure is adiagrammatic view of a control system embodying my invention.

Referring to the drawing by characters of reference, A designatesgenerally a temperature responsive or thermostatic switch having a baseor supporting member of metal or other electric conducting material onwhich is pivotally mounted, as at 2, an adjustable supporting arm 3 bywhich the range of operation of the temperature responsive switch may beregulated. The arm 3 is electrically connected by its pivotal support tothe base I. Rigidly fixed at one end to the free end of the arm' 3, asat 4, there is a bimetal switch blade having its free end portiondefining an armature and carrying a contact member 6. Mounted on thebase I adjacent the free end of the blade 5 there is a supporting block1 of metal or other electric conducting material which is electricallyinsulated from the base i. The block I is provided with a contact member8 cooperable with the contact member 6 to make and break an electriccircuit to be described. The block "I is also provided with a permanentbar magnet 9 which is adjustably supported therein and which iscooperable with the armature portion of the blade 5. Adjustment of themagnet 9 relative to the blade 5 to vary the air gap when contact ismade determines the differential of operation of the switch andpredetermines the maximum temperature differential of the blade at whichcontact will be made and broken. The switch A is electrically connectedto a source of current supply B by a lead wire Ill connected to theblock 'I. The source B is shown as a transformer having its primarysupplied by lead wires II and having one terminal l2 of its 5 secondaryconnected to the lead wire [0. It is to be noted that the current may besupplied directly from a source of high potential without affecting theoperation of my system which is shown as low voltage merely forillustration. The switch A means C may be a relay or any otherelectrically operated means C which is shown as a solenoid operatedvalve solely by way of example as the means C may be a relay or anyother electrically energized or operated means. The means C is providedwith an electrically energized operating coil l3 which has one terminalI4 connected by a lead wire l5 to the other post or terminal l6 of thetransformer secondary. From the other terminal I? of the coil 13 thelead wire l8 connects to the metal switch base I, as at l9, so that thecoil 13, the switch A and the transformer secondary are in seriescircuit. Also in series circuit with the switch A and in parallelcircuit or multiple with the electrically operated means C, there is avariable electric resisting means or rheostat D. The rheostat D isprovided with a segmental contact plate 20 having an operating knob 2|and cooperable with a row of spaced contact or terminal members 22. Acontinuous resistance wire or similar means 23, which is of zig-zagform, has the return bent portions along one side connected to the spacemembers 22 and has the return bent portions along its other sideelectrically connected to a conductor bar 24 so that clockwise rotationof plate 20 in the direction of the arrow will cut out or decrease theelectrical resistance of the rheostat. The plate 20 is electricallyconnected by a lead wire 25 to the lead wire 88 at terminal post it andthe bar.24 is electrically connected by a lead wire 26 to the lead wirel5 at the terminal post it so that the coil I3 and the rheostat D are inparallel circuit with each other. The operation of my system is asfollows: Considering first the operation independent of rheostat D, thethermostatic switch A being in closed circuit position as shown, thecoil 63 of the electrically operated means C will be energized andcurrent will flow from the transformer secondary through the coil l3 andthe switch blade El and thence back to the transformer secondary. Due tothe electrical resistance of the blade 5, the blade will be heated bythe current flowing therethrough to a temperature somewhat higher thanthe temperature of the air or other medium' surrounding the blade and towhich it is subjected. The heating of the blade will be dependent uponthe resistance of the blade which is a constant factor and upon theresistance offered by the coil I 3. apparent that the movement of bladeto open circuit position is determined by the heat imparted to the bladefrom the surrounding air and from the current flow through the blade 5,and that closing movement of blade 5 is dependent solely on heatimparted to the blade from the surrounding air or other medium.Therefore for any given or predetermined resistance of the coil l3 thedifferential operation of the switch may be regulatedby adjustment ofthe magnet 9. However, assuming that the magnet 9 has been adjusted toprovide a desired difierential of operation of the switch with a certainor determined circuit load, it will be apparent that change in the loador resistance of the coil l3 as by the use of a coil having a difl'erentresistance will result in a change in the current flowing through theblade 5 so that there will be a change in the heating of the blade. Anychange in the current flow through the blade will result in a change inthe differential of operation of the, switch for a given setting oradjustment of the magnet 9. Any such variation in the circuit load maybe compensated by means of the rheostat D which provides an additionalpath for current flow in series with the thermostatic switch so that thecurrent flow through the blade 5 may be maintained constant for anyvariation in the resistance of the coil I3 within the limits of thevariable resistance of the rheostat D. If, for example, the thermostaticswitch is adjusted by the magnet 9 to provide a two degree differentialof operation of the switch between the temperatures at which contactwill be made and broken for a power consumption in the circuitcomprising the switch and the means C controlled thereby of say 25watts, then if the resistance of the coil I3 is changed or anelectrically operated means C having a different resistance is employedsuch that the power consumption is less than 25 watts, less resistancemay be put in parallel circuit with the means C and in series with thethermostatic switch by means of the rheostat D by adjusting knob 2| toprovide additional current paths so that the current flow through theblade 5 may be maintained constant thereby maintaining constant thedifferential of operation of the switch A.

The system is also operable to regulate the operation of the switch Awithin the maximum diflerential, set or determined by the magnet 9.Assuming that the switch is adjusted by the magnet 9 to have a twodegree differential of operation when the power consumption oflthecircuit including the means C is 25 watts, then by adjusting therheostat D so that there will be a greater current flow through theblade 5 the heating of the blade by the current flowing therethroughwill be increased with the result that the differential of operation ofthe switch A will be decreased. By increasing the current flow throughthe blade so that the temperature of the blade when the switch is closedis heated say two degrees above the temperature of the surroundingmedium, which temperature differential is also the differential ofoperation determined by the magnet 9, then the operation of the switch Awill be fully compensated so that contact will be broken upon anyincrease from a given tempera ture at which the switch is set to close.It will also be apparent that the switch may be over- It will thereforebe compensated by increasing the current flow through the bladesufllciently so that the temperature rise of the blade due to electricalheat-' ing when the switch is closed will be greater than the maximumdifferential of operation determined by the setting of the magnet 9.With such an adjustment of the current flow through blade 5, the switchwill intermittently open and close until the temperature of the mediumsurrounding the blade has decreased below the range setting of theswitch by an amount equal to the difference between the differential ofoperation of the switch as determined by the magnet 9 in degrees oftemperature and the number of degrees temperature to which the blade isheated by the current flow-therethrough.

It will also be noted that when the switch operates to make circuit onincrease of temperature of the surrounding medium as would occur inconnection with control of refrigerating apparatus or the like, thedifferential of operation due to heating of the blade 5 by current flowtherethrough will be added to the differential of operation determinedby the setting or adjustment of the magnet 9. If therefore for a givencurrent flow through the blade, the magnet 9 is adjusted to provide forbreaking of circuit at a differential of operation of say two degreesbelow the temperature at which contact is made, then decreasing of thecurrent flow through the blade by means of the rheostat D will decreasethe differential of operation of the switch A. If the current flowthrough the blade is increased by adjustment of the rheostat D, thedifferential of operation will be increased to cause a greaterdifferential of operation of the switch than was.

determined by the setting of the magnet 9, that is, ,will further lowerthe temperature point at which contact is broken without changing thedegree of temperature at which. contact is made.

From the foregoing description, it will be apparent that the rheostat Dis also operable when the thermostatic switch A makes circuit onincrease of temperature to maintain the differential of operation of theswitch constant with changes in the resistance of the means C controlledby the switch.

What I claim and desire to secure by Letters Patent 01' the UnitedStates is:

1. In a temperature controlling system, a thermostat responsive toambient temperature, means cooperable with said thermostat determiningthe temperature difl'erentlal between opening and closing response ofsaid thermostat to ambient temperature, an electrically operated meanshaving a source oi current supp y and comprising the circuit load, saidthermostat having switch contacts controlling current supply to saidelectrically operated means, said thermostat having a resistance tocurrent flow acting to heat the thermostat when said contacts areclosed, and electrical resistance means in parallel circuit with saidload for regulating the heating of said thermostat thereby to vary thethermostat differentiai determined by said first-named means.

2. In a temperature controlling system, a thermostat responsive toambient temperature and having switch contacts, an electrically operatedmeans in circuit with said contacts and controlled by said thermostat,magnetic means cooperable with said thermostat and opposing separationof said contacts to provide quick contact breaking movement, saidmagnetic means establishing a temperature diil'erential of operation,said thermostat having a resistance to cur- 5 means and cooperable withsaid rent flow acting to heat-the'thermostat in accordcooperable withsaid thermostat and opposing separation of said contacts, the heating ofsaid thermostat by current flow through said resistof said ance varyingwith change in resistance electrically operated means, and electricalresistance means in parallel circuit with said electrically operatedmeans, said last-named means acting to compensate for variation inresistance of said electrically operated means thereby to maintain aconstant differential oi operation of 10 said thermostat.

EARNEST J. DILLMAN.

thermostat when said contacts are closed. means CERTIFICATE OFCORRECTION,

J atent No. 2,o6 l,536, I November 17, 1936.

EABNEST J. DILLMAN.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows Page 1,second column, line 11, for the words "means 0 may be a relay or anyother" read serves to control the operation of an; and that the saidLetters Patent should be read with this correction therein that the samemay conform to Seal) the record oi thegc'ase in the Patent OfficersSigned and-sealed this 9th day of March, A. o. 195?.

- I o Henry Van Arsdale 1 I Acting Commissioner of Patents.

